This invention relates to an apparatus for, and a method of, recording, with radiation from a laser light beam, a plurality of preselected patterns (either transparent and/or opaque to a laser light beam) on a target made of high gain retroreflective sheeting of the exposed-lens type; and, thereafter, selectively viewing any one of the recorded patterns, with the naked eye (i.e., without illumination by a laser light beam).
As a preliminary matter, and with reference to FIG. 1, it is to be noted and understood that the phrase "high gain retroreflective sheeting of the exposed-lens type", or the like, is intended to mean herein, as it does in the prior art, sheeting 10, FIG. 1, having a plurality of transparent glass microspheres, such as 11A-11H, inclusive, FIG. 1, that are partially embedded in a binder layer, such as 12, FIG. 1, and that are partially exposed above the binder layer, as shown in FIG. 1, with a reflective layer, such as 13, FIG. 1, adjacent to and disposed behind the embedded surface of each of the plurality of transparent glass microspheres, wherein the binder layer 12 is pigmented with carbon black 12A (to minimize any stray light that impinges upon the sheeting 10), and wherein the reflective material 13 is a vapor-deposited layer of aluminum.
Such sheeting 10, FIG. 1, is made by, and is commercially available from, the Minnesota Mining and Manufacturing Company of Saint Paul, Minn. 55133. The sheeting is well known in the art as "SCOTCHLITE" brand reflective sheetings "High Gain" No. 7610 and No. 7611.
An early and basic representative sheeting of this type, such as 10, FIG. 1, is shown and is described in U.S. Pat. No. 2,326,634, issued to Melvin L. Gebhard et al on 10 Aug. 1943, and reference thereto and reading thereof is recommended. It is here to be noted that two principal differences between sheetings No. 7610 (and No. 7611) and the basic sheeting described in U.S. Pat. No. 2,326,634 are: (1) the reflective layer, such as 13, FIG. 1, of the sheeting 10, FIG. 1, referred to in this application is a vapor-deposited layer of aluminum, rather than the aluminum foil shown and described in U.S. Pat. No. 2,326,634; and (2) the binder layer, such as 12, FIG. 1, is pigmented in carbon black, whereas such is not the case of the binder shown and described in U.S. Pat. No. 2,326,634. It is also to be noted that I am merely the user of this type of sheeting, such as 10, FIG. 1; and, that I am not in any way the inventor or improver thereof. As far as I know, sheetings No. 7610 and No. 7611 are proprietary to the Minnesota Mining and Manufacturing Company; and, these two particular sheetings appear to differ from each other only as to adhesive characteristics of any backing material, and such characteristics are of no importance to my invention.
My invention, which comprises an apparatus and a method, is the result of a phenomenon that I have discovered, namely: that, if a pattern is recorded with and by a laser light beam that is radiated on a target made of high gain retroreflective sheeting of the exposed-lens type, while the target is positioned in any arbitrarily previously chosen angle with reference to the longitudinal (i.e., principal) axis of the laser light beam, then the recorded pattern (i.e., image) which is recorded on the target by structural alteration (i.e., modification) of the target material by the laser light beam radiation, can be seen thereafter with the naked eye if, and only if, the target is again positioned at that same angle. Stated a different way, I have found that, if a plurality of different preselected patterns are individually and separately recorded, at different angles, with the radiation from a laser beam on the same target of this type of sheeting, then each of the recorded patterns is visible only when viewed at the angle at which it was recorded by the laser light beam radiation on the target.
By the use of the discovery of this phenomenon, I am able with my inventive apparatus and method to attain many new, useful and unobvious results involving multiple images stored on the same target, or involving one image stored on multiple targets at different angles (e.g., animation), and the like.
I have, thereby, significantly advanced the state-of-the-art.